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Research Papers: Fundamental Issues and Canonical Flows

Control of Vortex Shedding From a Plate at Incidence Angles in the Range of 0–90 Deg

[+] Author and Article Information
Chuan Ping Shao

 China Jiliang University, Hangzhou 100080, Chinashaocp2005@yahoo.com.cn

Jian Zhong Lin

 China Jiliang University, Hangzhou 100080, Chinamecjzlin@public.zju.edu.cn

J. Fluids Eng 131(11), 111202 (Oct 27, 2009) (9 pages) doi:10.1115/1.4000303 History: Received November 24, 2008; Revised June 27, 2009; Published October 27, 2009

A thin strip cross-sectional element is used to suppress vortex shedding from a plate with a width to thickness ratio of 4.0 at incidence angles in the range of 0–90 deg and a Reynolds number of 1.1×104. The axes of the element and plate are parallel. The incidence angle of the element is 90 deg and the ratio of strip width to plate thickness is 0.5. Extensive measurements of wake velocities, together with flow visualization, show that vortex shedding from both sides of the plate is suppressed at incidence angles in the range of 0–55 deg if the element is placed at points in effective zones. Unilateral vortex shedding occurs if the element is applied at points in unilateral effective zones. The changes in sizes and locations of the effective and unilateral effective zones with the change in plate incidence are investigated, and the mechanism of the control is discussed. Two patterns of unilateral vortex shedding are observed. Pattern I occurs on the side where there is no element, and oppositely, pattern II occurs on the side where the element resides. A resonance model is proposed to illustrate the occurrence of pattern II unilateral shedding. The phenomenon of unilateral vortex shedding means that the vortex can be generated without strong interaction between the shear layers separated from the bluff body.

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Copyright © 2009 by American Society of Mechanical Engineers
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Figures

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Figure 1

Sketch of geometrical arrangements of the plate and control element: (a) arragement of the model test; (b) dimensions of the plate and strip element

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Figure 2

The control effect at α=0 deg: (a) without element; (b) with the element at X/H=2.0 and Y/H=1.2; (c) with the element at X/H =−2.0 and Y/H = 1.0; (d) with the element at X/H=2.0 and Y/H = 2.5; (e) with the element at X/H=−2.5 and Y/H=1.5; (f) with the element at X/H=0.0 and Y/H=0.5; (g) with the element at X/H=0.0 and Y/H=1.17; and (h) with the element at X/H=0.0 and Y/H=2.5

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Figure 3

The control effect at α=20 deg: (a) without element; (b) with the element at X/H=0.0 and Y/H=2.0; (c) with the element at X/H=3.5 and Y/H=−2.0; (d) with the element at X/H=3.5 and Y/H=2.0; (e) with the element at X/H=2.0 and Y/H=−2.0; and (f) with the element at X/H=3.5 and Y/H=1.8

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Figure 4

The control effect at α=30 deg: (a) without element; (b) with the element at X/H=3.7 and Y/H=−1.4; (c) with the element at X/H=3.7 and Y/H=−1.9; and (d) with the element at X/H=3.7 and Y/H=−3.0

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Figure 5

The suppression effect at α=40 deg: (a) without element; (b) strip element at X/H=4.0 and Y/H=−2.5; (c) strip element at X/H=4.5 and Y/H=3.5; and (d) strip element at X/H=4.5 and Y/H=−3.5

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Figure 6

The suppression effect at α=55 deg: (a) without element; (b) with the element at X/H=3.8 and Y/H=2.2

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Figure 7

The suppression effect at α=90 deg and Re=1.1×104: (a) without element; (b) with the element at X/H=4.0 and Y/H=5.0

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Figure 8

Power spectra of fluctuating velocities at points downstream the plate at α=0 deg with and without element

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Figure 9

Power spectra of fluctuating velocities downstream the plate at α=20 deg without element and with the element at X/H=3.5 and Y/H=1.6–2.0

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Figure 10

Power spectra of fluctuating velocities at points downstream the plate at α=30 deg with the element applied at points X/H=3.7 and Y/H=−1.4–−3.0

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Figure 11

Power spectra of fluctuating velocities at points downstream the plate at α=30 deg without element and with the element at X/H=2.7 and Y/H=3.1

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Figure 12

E and I-UE zones at different angles α

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Figure 13

Sketch of resonance model to show the pattern II unilateral vortex shedding: (a) flow in the first half period; (b) flow in the second half period

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